Hugh Trevor-Roper (1914-2003) was a British historian best known as the author of The Last Days of Hitler (1947). He wrote extensively on Nazi Germany and on England in the 16th and 17th centuries. His Ten Commandments for History Writers is lengthy, but well worth studying and taking to heart. It is written in the English of the King James Version of the Bible, which he handles accurately and admirably. For those of you in the TL:DR crowd, I’ll summarize by saying that he stresses writing in an orderly manner, with clarity and precision, and always keeping the needs of the reader in mind.

I particularly like commandments eight and nine: visualize your metaphors and listen to the sound of your words. Reading your work aloud is always helpful.

1. Thou shalt know thine own argument and cleave fast to it, and shalt not digress nor deviate from it without the knowledge and consent of the reader, whom at all times thou shalt lead at a pace which he can follow and by a route which is made clear to him as he goeth.

2. Thou shalt respect the autonomy of the paragraph, as commanded by the authority and example of the prophet Edward Gibbon, for it is the essential unit in the chain of argument. Therefore thou shalt keep it pure and self-contained, each paragraph having within it a single central point to which all other observations in it shall be exactly subordinated by the proper use of the particles and inflections given to us for this purpose.

3. Thou shalt aim always at clarity of exposition, to which all other literary aims shall be subordinated, remembering the words of the prophet commandant Black, “clarté prime, longueur secondaire.” [clarity is primary, length secondary] To this end thou shalt strive that no sentence be syntactically capable of any unintended meaning, and that no reader be obliged to read any sentence twice to be sure of its true meaning. To this end also thou shalt not fear to repeat thyself, if clarity require it, nor to state facts which thou thinkest as well known to others as to thyself, for it is better to remind the learned than to leave the unlearned in perplexity.

4. Thou shalt keep the structure of thy sentences clear, preferring short sentences to long and simple structures to complex, lest the reader lose his way in a labyrinth of subordinate clauses; and, in particular, thou shalt not enclose one relative clause in another, for this both betrays crudity of expression and is a fertile source of ambiguity.

5. Thou shalt preserve the unities of time and place, as commended by the High Priest Nicholas Boileau, placing thyself, in imagination, in one time and place, and distinguishing all others to which thou mayest refer by a proper use of tenses and other forms of speech devised for this purpose; for unless we exploit the distinction between past and pluperfect tenses, and between imperfect and future conditional, we cannot attain perfect limpidity of style and argument.

6. Thou shalt not despise the subjunctive mood, a useful, subtle and graceful mood, blessed by Erasmus and venerated by George Moore, though cursed and anathematised by the Holy Inquisition, Pravda, and the late Lord Beaverbrook.

7. Thou shalt always proceed in an orderly fashion, according to the rules of right reason; as, from the general to the particular when a generality is to be illustrated, but from the particular to the general when a generality is to be proved.

8. Thou shalt see what thou writest; and therefore thou shalt not mix thy metaphors. For a mixed metaphor is proof that the image therein contained has not been seen with the inner eye, and therefore such a metaphor is not a true metaphor, created by the active eye of imagination, but stale jargon drawn up from the stagnant sump of common-place.

9. Thou shalt also hear what thou writest, with thine inner ear, so that no outer ear may be offended by jarring syllables or unmelodious rhythm; remembering therein with piety, though not striving to imitate, the routines of Sir Thomas Browne and the clausulae of Cicero.

10. Thou shalt carefully expunge from thy writing all consciously written purple passages, lest they rise up to shame thee in thine old age. [This is otherwise known as “kill your darlings.”]

(Lord Dacre of Glanton [Hugh Trevor-Roper], 1914-2003; historian – Christ Church College, Oxford, 1946-57; and Regius Professor of History and Fellow of Oriel College, Oxford, 1957-80; Master of Peterhouse, Cambridge, 1980-87)